A new survey released Thursday found that just one in four people who signed up for Obamacare through mid-February were previously uninsured.

The report by consulting firm McKinsey & Co. estimated that 27 percent of those signing up for health care through federal and state exchanges had lacked health care coverage. Of the previously uninsured, 53 percent said they had paid their first month's premium.

In total, just one in 10 of those lacking insurance said they had enrolled in a plan through the new marketplaces.

The central premise of President Obama's signature domestic achievement is that it would provide insurance to millions of Americans lacking any form of health care coverage.

The administration has been unable to quantify how many people signing up for Obamacare had previously obtained insurance coverage. Senior administration officials have promised such information but have been unable to identify how they would provide it.

Republicans contend that rather than significantly shrinking the ranks of the uninsured, Obamacare is simply forcing people to ditch their old insurance plan for a new one.

Consumers have just a little more than three weeks to obtain health insurance or pay a fine. The White House has predicted a late surge in enrollment just prior to the March 31 deadline.

The president recently announced that 4 million people had signed up for Obamacare, an improvement from the botched rollout of the exchanges, but still off the pace needed to meet the administration’s goal of signing up 7 million people by the end of March.